I was under the impression that the Yamaha gp1800 does over 70 mph. Is that incorrect?
Yes, there is basically an agreement between the manufacturers and the coast guard that the top speed will be electronically limited to 67 mph. Higher speeds are just a tuner away.
From a PWC Today Article...
"The “fastest” production personal watercraft on the planet may not ever get the chance to really prove it in stock condition, at least not in the United States. That’s because years ago, as manufacturers seemingly jumped into a full-on horsepower war, the Coast Guard registered its concern. Go too much further and the Coasties warned they may have to step in and pay a little more attention to the speed issue, perhaps try to enact limits to keep things from getting out of hand. What resulted was the infamous “handshake agreement,” an informal pact between manufacturers and the USCG to limit top speed to 65 mph. In today’s age of electronically controlled engines, it’s a relatively easy thing to do. Though the engines may be capable of more, they’re in effect limited, governed to produce only so much power.
So, an apples-to-apples comparison of the highest-horsepower models is often inconclusive, as competitors are all programmed to peak at roughly the same speed.
Of course, that magic number 65 is somewhat of a moving target. For starters, in the initial agreement the Coast Guard gave manufacturers a leeway of two miles per hour. Production tolerances, conditions, load, many things can make that number 65 vary on any given day."